WestAbstract
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WestAbstract
The core principles of collecting good quality data from site for creating CCTV inspection reports including some explanations of how to avoid common mistakes.
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The PLR Naming Convention
Most global drainage inspection standards include a system for naming pipes based on either the upstream manhole ID or a combination of both the upstream and downstream manhole IDs. The Manual of Sewer Condition Classification (MSCC) defines the naming convention for WRc pipe and sewer inspection using the Pipe Length Reference (PLR) system at all times:
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This works well in Infonet and helps with connectivity analysis, but there is no concept of this in the WRc MSCC data stream which is why using this value to create PLRs is not recommended.
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Good Site Drawings
Everything described above regarding avoiding problems with data in software applications can be avoided by taking care and time to create good quality site drawings. The process described here considers a domestic CCTV inspection but the recommended logical approach can be extended to any type of CCTV inspection.
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Notice in the drawing we have used red lines for foul drains and blue for surface water objects. There is not hard and fast recommendation for this and different water companies use different colours for this so you can be fluid, but it is advisable to at lease have some coloured pens to hand for this reason, particularly where there are separate foul and surface water systems at the site.
Step 3 - add some annotations to the drawing to clearly identify each node point on the site and do not forget to make up node IDs for ‘invisible’ connector nodes. Add some information about the physical attributes of the pipes and nodes based on observation. All of this will make life a whole lot easier when it comes to actually carrying out the CCTV inspection:
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Site drawing part 3.
Step 4 - crack on with the CCTV inspection. Life will be really easy now when it comes to entering the upstream and downstream nodes for each pipe that you camera. Just be a little careful of the connector nodes. The WRc inspection standard requires that pipe inspections are done from end to end, so in the example above, we could inspect IC2 - IC3 either upstream or downstream, and we would never inspect IC2 to CN1 or IC3 to CN2. We would simply inspect the whole pipe and add the appropriate junction or connection observation does at CN1 and CN2 as required and carry on until the end of the pipe at the next chamber or node point.
If we needed to inspect the pipe from WC1 to CN1 in a situation like this where there is no chamber at CN1, then we need to practice the ‘Indian Rope Trick' with the camera where we tie a piece of rope to the spring behind the camera head, push the camera up from IC3 to CN1 without any recording and with the rope attached and then push the camera cable while pulling the rope so that the camera flicks into the junction. Now, we pause, set the distance counter to zero on the camera and create a new clean inspection on the lateral (this is a true lateral - a pipe coming into a manhole is not a lateral) WC1 to CN1, upstream.
Step 4 - make some notes based on what you have seen and deduced during the inspection for the office:
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Site drawing part 4.
That’s it, your job as a CCTV surveyor is complete provided that the video files and data that you have recorded on your CCTV camera match up with this drawing. Based on the information reported here, the office rehab manager can either go with your recommendations or create their own, but regardless of which way they go, they have enough information in the video files, pictures and (most importantly) the very good site sketch to make all the good and proper quotations needed for this job.
Understanding STC25 Manhole References
It is common when working with water company asset records to see STC25 manhole references like NZ24567401 (made up example) and although this seems like a mad set of numbers and letters, the way these are constructed is actually quite simple and is described in Appendix A of the MSCC.
The first 8 digits of this manhole reference represent a 100m square grid on the ground by GIS coordinates and the last 2 numbers are a numeric counter, so 01 is the first manhole inside this 100m grid, followed by 02, 03 etc and a maximum of 100 manholes 00-99 (extremely unlikely) in this 100m grid space.
Some water companies reserve 00-49 for foul water manholes and 50-99 for surface water manholes but this is not set in stone across the UK - you should check with your client on how they handle this.
To understand the STC25 reference, we must split it up into its 5 constituent parts:
NZ 24 56 7 4 01
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NZ = the 100km grid tile that you are currently in as described and specified by the Ordnance Survey. Remember 100km = 100,000 metres.
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24 = the 24th kilometre across the NZ box from the bottom left corner starting at 00.
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56 = the 58th kilometre up the NZ box from the bottom left corner starting at 00.
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7 = the 7th 100m segment across the km grid square starting at 00.
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4 = the 4th 100m segment ip the km grid square starting at 00.
01 = numeric counter as described previously.
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OS grid tiles.
From this, we can deduce that the NZ 100km grid tile is in the North East of England, and if we count 24Km East from the bottom-left corner of the tile and 56Km North from the bottom-left corner of the tile, then we hit the red cross:
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The NZ 100Km tile.
The red cross is the location of the 1km grid square and then we split this 1Km square up into 100m square tiles to find the 7th square across and the 4th tile up from the bottom left corner.
Using this system we can define the geometric coordinates of every mahole in the country to within a single 100 x 100 metre square.
What this means for regular CCTV operators is;
you can do what you want with the last 2 characters, they are unique identifiers only, and
you cannot assume what the correct values for the first 8 characters are because you may be standing on a prescribed 100m square right now but if you take one step to the right or left then you could be in a different square and you would never know it. There are no golden lines on the ground where these square start and end.
WinCan VX Map includes an option to click on a point on the screen against a given background location plan and the appropriate STC25 reference will be generated for you. How does it do this? Because we know the coordinates where the mouse was clicked on the screen and the first 8 digits are geo-spacial so they are not in a question or open to modification by the user.
Given that the Water and Sewerage Companies (WaSCs - pronounced Wazzucks 😃) usually use 2 numeric digits for the last 2 values when we are plotting uncharted assets, we cannot be absolutely sure in any 100m grid square that the last 2 digits ‘01’ have already been used by the WaSC so an easy solution when using WinCan Map VX is to let the software create the correct STC25 reference and then edit the last 2 character sonly to 2 letters rather than 2 numbers. The best suggestion for this to prevent duplicates on the client’s mapping system is to use your initials for the first uncharted, so the first manhole in the 100m grid might be JG (if that’s your initials), then JH, JI, JK etcand surface water systems at the site.
Step 3 - add some annotations to the drawing to clearly identify each node point on the site and do not forget to make up node IDs for ‘invisible’ connector nodes. Add some information about the physical attributes of the pipes and nodes based on observation. All of this will make life a whole lot easier when it comes to actually carrying out the CCTV inspection:
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Site drawing part 3.
Step 4 - crack on with the CCTV inspection. Life will be really easy now when it comes to entering the upstream and downstream nodes for each pipe that you camera. Just be a little careful of the connector nodes. The WRc inspection standard requires that pipe inspections are done from end to end, so in the example above, we could inspect IC2 - IC3 either upstream or downstream, and we would never inspect IC2 to CN1 or IC3 to CN2. We would simply inspect the whole pipe and add the appropriate junction or connection observation does at CN1 and CN2 as required and carry on until the end of the pipe at the next chamber or node point.
If we needed to inspect the pipe from WC1 to CN1 in a situation like this where there is no chamber at CN1, then we need to practice the ‘Indian Rope Trick' with the camera where we tie a piece of rope to the spring behind the camera head, push the camera up from IC3 to CN1 without any recording and with the rope attached and then push the camera cable while pulling the rope so that the camera flicks into the junction. Now, we pause, set the distance counter to zero on the camera and create a new clean inspection on the lateral (this is a true lateral - a pipe coming into a manhole is not a lateral) WC1 to CN1, upstream.
Step 4 - make some notes based on what you have seen and deduced during the inspection for the office:
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Site drawing part 4.
That’s it, your job as a CCTV surveyor is complete provided that the video files and data that you have recorded on your CCTV camera match up with this drawing. Based on the information reported here, the office rehab manager can either go with your recommendations or create their own, but regardless of which way they go, they have enough information in the video files, pictures and (most importantly) the very good site sketch to make all the good and proper quotations needed for this job.
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Understanding STC25 Manhole References
It is common when working with water company asset records to see STC25 manhole references like NZ24567401 (made up example) and although this seems like a mad set of numbers and letters, the way these are constructed is actually quite simple and is described in Appendix A of the MSCC.
The first 8 digits of this manhole reference represent a 100m square grid on the ground by GIS coordinates and the last 2 numbers are a numeric counter, so 01 is the first manhole inside this 100m grid, followed by 02, 03 etc and a maximum of 100 manholes 00-99 (extremely unlikely) in this 100m grid space.
Some water companies reserve 00-49 for foul water manholes and 50-99 for surface water manholes but this is not set in stone across the UK - you should check with your client on how they handle this.
To understand the STC25 reference, we must split it up into its 5 constituent parts:
NZ 24 56 7 4 01
NZ = the 100km grid tile that you are currently in as described and specified by the Ordnance Survey. Remember 100km = 100,000 metres.
24 = the 24th kilometre across the NZ box from the bottom left corner starting at 00.
56 = the 58th kilometre up the NZ box from the bottom left corner starting at 00.
7 = the 7th 100m segment across the km grid square starting at 00.
4 = the 4th 100m segment up the km grid square starting at 00.
01 = numeric counter as described previously.
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OS grid tiles.
From this, we can deduce that the NZ 100km grid tile is in the North East of England, and if we count 24Km East from the bottom-left corner of the tile and 56Km North from the bottom-left corner of the tile, then we hit the red cross:
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The NZ 100Km tile.
The red cross is the location of the 1km grid square and then we split this 1Km square up into 100m square tiles to find the 7th square across and the 4th tile up from the bottom left corner.
Using this system we can define the geometric coordinates of every mahole in the country to within a single 100 x 100 metre square.
What this means for regular CCTV operators is;
you can do what you want with the last 2 characters, they are unique identifiers only, and
you cannot assume what the correct values for the first 8 characters are because you may be standing on a prescribed 100m square right now but if you take one step to the right or left then you could be in a different square and you would never know it. There are no golden lines on the ground where these square start and end.
WinCan VX Map includes an option to click on a point on the screen against a given background location plan and the appropriate STC25 reference will be generated for you. How does it do this? Because we know the coordinates where the mouse was clicked on the screen and the first 8 digits are geo-spacial so they are not in a question or open to modification by the user.
Given that the Water and Sewerage Companies (WaSCs - pronounced Wazzucks 😃) usually use 2 numeric digits for the last 2 values when we are plotting uncharted assets, we cannot be absolutely sure in any 100m grid square that the last 2 digits ‘01’ have already been used by the WaSC so an easy solution when using WinCan Map VX is to let the software create the correct STC25 reference and then edit the last 2 character sonly to 2 letters rather than 2 numbers. The best suggestion for this to prevent duplicates on the client’s mapping system is to use your initials for the first uncharted, so the first manhole in the 100m grid might be JG (if that’s your initials), then JH, JI, JK etc.
HADDMS Version of STC25 References
HADDMS also uses the same type of node referencing as the MSCC, but they have 2 additional characters in the geometric part of the string, and they are not limited to only 10 characters.
So, with HADDMS numbering, we are focusing down to a 10m grid rather than a 100m grid and a typical HADDMS node reference might look like NZ2456_7348a:
NZ 24 56 _ 73 48 a
NZ = the 100km grid tile that you are currently in as described and specified by the Ordnance Survey. Remember 100km = 100,000 metres.
24 = the 24th kilometre across the NZ box from the bottom left corner starting at 00.
56 = the 58th kilometre up the NZ box from the bottom left corner starting at 00.
_ = fixed text character.
73 = the 73rd 10m segment across the km grid square starting at 00.
48 = the 48th 10m segment up the km grid square starting at 00.
a = alpha node counter inside this 10m grid.
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